Instead, if the spectrum is formed from thermal Comptonisation from
self-produced cyclo-synchrotron photons in the hot flow then there can
be complex time variability properties imprinted via propagating
fluctuations through an inhomogeneous flow ([1]};
[2]}). Whether these can indeed explain the
anti-correlation between optical and X-ray by such spectral pivoting
[3]} remains to be seen.
